Consciousness(citta) has a single characteristic as the cognizing of an object, a characteristic that remains the same in all its diverse manifestations, the Abhidhamma distinguishes citta into a variety of types. These types, also called cittas, are reckoned as 89 or by a finer method of differentiation, as 121. [See Table 1.1. CMA I, p. 28.]

CMA I, p. 31: Both wholesome and unwholesome consciousness constitute kamma, volitional action. These cittas or states of consciousness that arise through the ripening of kamma are called resultants (vipaaka).

CMA III, p. 122-124: The eighty-nine types of consciousness are classified by ways of function (kicca). The Abhidhamma posits altogether fourteen functions performed by different kinds of consciousness. These are exercised either at distinct phases within the cognitive process(3-13) or on occasions when consciousness is occurring outside the cognitive process, that is, in process-freed consciousness (1,2,14).

(1) Rebirth-linking(pa.tisandhi): This function exercised at conception is called rebirth-linking because it links the new existence to the previous one. The consciousness that performs this function occurs only once in the individual existence, at the moment of rebirth.

(2) Life-continuum (bhavanga): The word bhavanga means factor(anga) of existence(bhava), that is, the indispensible condition of existence. Bhavanga is the function of consciousness by which the continuity of the individual is perceived through the duration of any single existence, from conception to death. After the pa.tisandhicitta has arisen and fallen away, it is then followed by the bhavangacitta, which is a resultant consciousness of the same type as pa.tisandhicitta but which performs a different function, namely, the function of preserving the continuity of the individual existence. Bhavangacittas arise and pass away every moment during life whenever there is no active cognitive process taking place. This type of consciousness is most evident during most dreamless sleep, but it also occurs momentarily during waking life countless times between occasions of active cognition.When an object impinges on a sense door, the bhavanga is arrested and an active cognitive process ensues for the purpose of cognizing the object. Immediately after the cognitive process is completed, again the bhavanga supervenes and continues until the next cognitive process arises. Arising and perishing at every moment during this passive phase of consciousness, the bhavanga flows on like a stream, without remaining static for two consecutive moments.

(3) Adverting(aavajjana): When an object impinges at one of the sense doors or at the mind door, there occurs a mind-moment called bhavangacalana, vibration of the life-continuum, by which the bhavanga consciousness "vibrates" for a single moment. This is followed by another moment called bhavanga-uppacheda, arrest of the life-continuum, by which the flow of the bhavanga is cut off. Immediately after this, a citta arises turning to the object, either at one of the five physical sense doors or at the mind door. This function of turning to the object is termed adverting.